Degreasers or defluxers are commonly used for degreasing, precision cleaning and defluxing of various articles, such as removing solder flux from printed circuit boards. The articles are typically conveyed through one or more zones within the degreaser/defluxer for contact with a solvent, such as fluorocarbon based CFC-113, manufactured by Genesolv/Baron-Blakeslee, Melrose Park, Ill., a division of Allied Signal, Inc., assignee of the present invention. The articles are cleaned by entering the degreaser on a conveyor through an entrance end thereof for passage through a solvent vapor zone, immersion within a liquid solvent, solvent spraying, or any combination thereof. The articles are then conveyed from the degreaser/defluxer through an exit end.
The entrance and exit ends of conventional in-line conveyer type degreaser and defluxer equipment are generally in open communication with both the ambient environment and the solvent within the equipment. Consequently, there is a loss of solvent from within the equipment to the surrounding environment caused by solvent vapor being carried off by normal air movement; this problem is exacerbated by air drafts entering the equipment through the entrance and/or exit ends and creating turbulence therewith.
Solvent vapor loss also occurs by vapor diffusion as the solvent covered articles exit the equipment. This evaporation problem is primarily caused by the relatively high ambient temperature conditions prevailing at the entrance and exit ends of the degreaser/defluxer. Air at ambient temperature entering the degreaser/defluxer through the entrance or exit ends also upsets the control temperature environment within the equipment (e.g., the use of chill coils which create a low temperature inversion blanket over a hotter vapor zone region in the degreaser/defluxing tank, such as disclosed in U.S. Pat. No. 4,261,111 to Rand). In addition, the relatively humid ambient air creates undesirable moisture within the tank which interferes with the defluxing/degreasing process.
The use of CFC-113 and FREON type solvents and vapor diffusion thereof into the environment also contributes to undesirable stratospheric ozone depletion. Consequently, it is expected that HCFC type solvents, which affect the environment significantly less than the CFC-113 and FREON type solvents, will replace the latter in accordance with environmentally safe operating principles. However, since these new HCFC solvents boil at much lower temperatures (82.degree. F.-86.degree. F.) than the above solvents being currently used, solvent loss as a result of vaporization is likely to increase.